This project is a continuation of our development of a system for direct scanning gel chromatography (DSGC). The DSGC system currently works with a log ratio output of the signals from two photomultiplier tubes: one to provide a reference for light source stability, the other to measure absorbancy through the scanned column. The output is interfaced to a PDP 1104 computer which stores and manipulates data under program control. Output is finally directed to an X-Y plotter. DSGC will be applied to study of associating protein systems including hexokinase in the presence of its various substrates, and to nitrogenase, in the presence or absence of substrates. Observed scanned spectra will be compared to computer simulations of the same scans to verify the reliability of the model of protein association chosen to apply to the experimental systems. Development of capabilities for scanning at various wavelengths by use of a stepping motor driven monochromator (already installed) and for scanning at variable speeds, is in progress. Experimental application of our previous findings on light scattering by different gel matrices is also a goal for this year. We will test the optical properties of some agaroses in the scanner although it is anticipated that they will scatter too much light for use in the ultraviolet.